Takeru Iwamura

A comparative study of glycerin fatty acid ester and magnesium stearate on the dissolution of acetaminophen tablets using the analysis of available surface area.

To study the effect of glycerin fatty acid ester (Poem TR-FB) concentrations on the dissolution rate of acetaminophen (APAP), the dissolution and disintegration behaviors of APAP tablets formulated using various lubricants were examined. The change over time in the available surface area of APAP (S(t)), which is in direct contact with solvent, was also analyzed using these dissolution data. In the dissolution tests, a retarded dissolution of APAP was not observed with TR-FB, whereas magnesium stearate (Mg-St), which is widely used as a lubricant, retarded the dissolution. However, no significant difference in the disintegration time between the two lubricants was observed. With regard to the time course of the S(t), Mg-St at 0.1% gave a maximum surface area value at 9.19 min (peak time); however, the profiles for APAP with Mg-St at greater than 0.5% showed downward curvature indicating a gradual decrease in surface area over time. Conversely, with TR-FB, even when its concentration was increased, the S(t) profile for APAP had a maximum value that was more than twice that of APAP with that of 0.5-3.0% of Mg-St. Scanning electron microscopy (SEM) observations showed that the differences in the dissolution rate and S(t) patterns between Mg-St and TR-FB could be explained by differences in extensibility deriving from their morphology. Therefore, it was concluded that TR-FB does not cause retardation of drug dissolution and may prove to be a superior alternative lubricant to Mg-St.

Identification and characterization of nanosized tripuhyite in soil near Sb mine tailings

Abstract In soil near tailings from an antimony (Sb) mine, we found micro-grains coated with an antimonyrich layer. These grains were characterized in detail using multiple advanced analytical techniques such as micro-X‑ray absorption near edge structure (μ-XANES), micro-extended X‑ray absorption fine structure (μ-EXAFS), micro-X‑ray diffraction (μ-XRD), transmission electron microscope (TEM), and electron probe microanalysis (EPMA). The EPMA showed that one soil grain (grain A) locally accumulated a large amount of Sb in the secondary phases (40-61 wt% Sb2O5) with significant Fe (20-28 wt% Fe2O3). The spatial distribution of Sb in the grain was similar to that of iron. Both Fe μ-XANES and μ-XRD of the Sb hot spots in grain A consistently showed that the secondary products were dominantly composed of ferric antimonate, tripuhyite (FeSbO4). Fits to the Sb K-edge μ-EXAFS of this phase showed second-neighbor coordination numbers -30% smaller than in bulk tripuhyite, indicating that the tripuhyite included in grain A is nanoparticulate and/or has a high structural disorder. The TEM analysis suggests that the particle size of tripuhyite in grain A was around 10 nm, which is consistent with the size range indicated by μ-XRD and μ-EXAFS. This is the first report showing tripuhyite with nanocrystallinity in natural soil to date.

Enhanced thermal conductivity in immiscible polyimide blend composites with needle-shaped ZnO particles

Novel blend composite films were prepared by mixing two kinds of immiscible polyimides (PIs), one containing sulfur (SD) and one containing fluorine (TF), with needle-shaped zinc oxide (n-ZnO) particles. Optical microscopy and cross-sectional SEM images revealed that vertical double percolation (VDP) structures were successfully formed in the PI blend films by spontaneous macro-phase separation. In the VDP structures, each phase is separately aligned along the out-of-plane direction, and the n-ZnO particles were selectively incorporated in the TF-rich phase. These blend composite films exhibited significantly higher thermal conductivity (TC) in the out-of-plane direction than blend composite films containing pyramidal ZnO (p-ZnO) particles. The wide-angle X-ray diffraction (WAXD) results revealed that the n-ZnO particles were more randomly oriented in the blend films than those in homopolymer films, in which the particles were preferentially aligned parallel to the film. The n-ZnO particles confined in the VDP structures and partially oriented along the out-of-plane direction contributed to the enhancement of the out-of-plane TC.

Suppressed Release of Clarithromycin from Tablets by Crystalline Phase Transition of Metastable Polymorph Form I

The pharmaceutical properties of clarithromycin (CAM) tablets containing the metastable form I of crystalline CAM were investigated. Although the dissolution rate of form I was higher than that of stable form II, the release of CAM from form I tablet was delayed. Disintegration test and liquid penetration test showed that the disintegration of the tablet delayed because of the slow penetration of an external solution into form I tablet. Investigation by scanning electron microscopy revealed that the surface of form I tablet was covered with fine needle-shaped crystals following an exposure to the external solution. These crystals were identified as form IV crystals by powder X-ray diffraction. The phenomenon that CAM releases from tablet was inhibited by fine crystals spontaneously formed on the tablet surface could be applied to the design of sustained-release formulation systems with high CAM contents by minimizing the amount of functional excipients.